initial agent-mgr: app builder platform MVP

Go API server + Preact UI + Claude Code adapter.
- App-centric model (ideas, not repos)
- AgentProvider interface for multi-agent support
- K8s pod lifecycle for sandboxed agent sessions
- Gitea integration (create repos, push branches)
- WebSocket streaming for live session output
- Woodpecker CI/CD pipelines (kaniko build + kubectl deploy)

.woodpecker/deploy.yaml

@@ -0,0 +1,16 @@
+depends_on:
+  - build
+
+when:
+  - event: [push, tag]
+    branch: main
+
+steps:
+  - name: deploy
+    image: bitnami/kubectl:latest
+    commands:
+      - kubectl -n agent-mgr set image deployment/agent-mgr agent-mgr=git.asp.now/platform/agent-mgr:${CI_COMMIT_SHA:0:8}
+      - kubectl -n agent-mgr rollout status deployment/agent-mgr --timeout=120s
+    backend_options:
+      kubernetes:
+        serviceAccountName: woodpecker-deployer